The
famous question "How long is a piece of string?" is
traditionally regarded as rhetorical rather than seeking an
answer. It's a question often asked to parallel the
unanswerability of another question. For example:

First
person: "However long are they going to take to get all this
sorted out?"

Second
person: "How long's a piece of string?!"

...which
means, in effect, "the question is about as answerable as a
question about the precise length of pieces of string in general".

It's
interesting, because the length of any specific piece of string
is directly measurable, whereas in the general case it's
indeterminate because of the wide range of non-standard lengths
of pieces of string.

This
(generality) is a crucial feature of the question "How long
is a piece of string?". If it were an enquiry about the
specific length of a definite section of twine, then it would be
readily answerable. The distance between one end of a string and
the other is clearly measurable. The cord has a definite length.
However, it's the generality of the question that gives it a
subtle mystique.

I
am often asked questions of an unusual nature, and I pride myself
on my ability to answer and to explain things in ways which
people can understand. If I hear someone happen to say in
conversation "how high's the moon?", I am tempted to
comment that it's about a quarter of a million miles. But
occasionally I have heard "How long's a piece of string?",
and before noticing the question is rhetorical I am ready to give
a brave attempt at answering the question!

Although
it may seem initially unanswerable, there are some facts which
help to solve the question. For a start, a piece of string can't
really be less than a quarter of an inch or it's not "a
piece of string" but more of a small sample from some string.
Similarly, any string longer than about 100ft isn't usually
classed as "a piece" of string, as it's more obviously
a reel of string. In fact, for any string to be A PIECE of string,
it tends to be a typical length. Pieces of string are typically
in their second or subsequent use, and have previously been used
in some application such as wrapping up a parcel or tying two
things together. As a result, the typical piece of string is in
the range of 1ft to 8ft, and if you were going to place a gambling spread-bet
of some type, you'd be best to go for a string length of about 3ft
6in or thereabouts.

In
a more mathematically factual answer, I'd say that the length of
a piece of string has a spread distribution of probability of a
continuous function with a graph... well I could imagine the type
of thing, with string length along the X axis and likeliness
along the Y axis, and a curve which starts low and builds up and
then levels off gradually. If someone was so inclined they could
put out a request for pieces of string and then measure them and
plot the results, which would give a graph somewhat similar to
the type of thing I can guess.

It's
not easy to express such an answer to the question "how long
is a piece of string" as a direct word-based answer, but a
good approximation would be: "the length of a piece of
string is usually about 4ft +/- 3ft".

Of
course it's not a perfect answer, and the distribution would have
a characteristic which is spread differentially either side of
the most likely length. This type of thing is not as uncommon as
you might think, for example electronic components are specified
as their nominal value +/- 10% or 20%, and colloquial terms such
as "faster than a speeding bullet" have an element of
expressiveness which often convey more than the statistical
figure.

Anyone
care for a thesis? 1. Collect random pieces of string in a
university string donations box. 2. produce a statistical survey.
3. profit? (there's a link in it for you, at least. write in)

Meanwhile,
question answering here goes quite well. Questions such as how logarithms work, what's
the density of mercury, how do
you hypnotise a chicken, and how to save money, are
answered here. Although I can't promise to answer everyone's
questions individually, if you ask a really good question there's
a good chance the question and answer will become a page here! To
send in a good question, see good
question. Hopefully some of
the answers should be of help generally.

Now
you've discovered this website, it might be a good idea to put it
in your favourites as there are a large number of pages of
interest like this!

Incidentally,
the Horizon programme "How Long is a Piece of String"
was not about the length of "a piece of string" where
that string is unknown (the classic form of the question), but
was instead about the science of measurement, for the purposes of
which a specific piece of string was measured using methods of
higher and higher accuracy, which involved explaining all kinds
of interesting things to do with the science of measurement, and
then to do with quantum physics. Interesting stuff.